Since every component of a conventional switch module of a power extension cord is connected by soldering, a casing of the switch module generally comes with upper and lower casings (as shown in FIG. 1A) engaged with each other and provided for containing related components. To achieve the insulation effect, the upper and lower casings are made of a plastic material, so that when a manufacturer solders each component, such as soldering a power conductive plate with a conductive clamping plate, the heat produced by the soldering process will be conducted to the casing quickly. Since the plastic material is not a heat-resisting material and may be melted easily, toxic gases are produced and the environment is polluted. After the casing is deformed by heat, the upper casing no longer can cover the lower casing tightly, and thus the defective rate will becomes larger. Furthermore, gases produced by heating the plastic material will be dispersed to other components having a lower temperature (without being affected by the soldering process) and solidified by the lower temperature and attached onto such components. As a result, the electric conductivity of the components will drop or other adverse effects will occur. Since the conventional switch module is assembled by a soldering process, the components are soldered manually one by one, and then the upper and lower casings are engaged to form the switch module, and thus the production rate is low. If an operator uses too little solder in the soldering process, an empty solder may occur and cause an unstable electric flow or even a power disconnection, or the soldering point may be weakened and loosened easily. If the operator uses too much solder, then an electric current passing through the switch module will be too large, and a large quantity of heat will be produced, such that the solder will be melted and the melted solder may flow to different soldering points of opposite polarities to result in a short circuit. Even worse, an accident may occur when using the switch module, and the reputation of the manufacturer and the safety of the user may be jeopardized.
To overcome the aforementioned problems, manufacturers design another switch module as shown in FIG. 1A, and the switch module comprises an upper casing 11, a lower casing 12, a press button 13, two power conductive plates 15 and two conductive clamping plates 16, wherein the lower casing 12 includes two corresponding support walls 121 protruded from the top of the lower casing 12, and disposed at a predetermined distance apart from both sides of the lower casing 12 for installing each power conductive plate 15 between each support wall 121 and both sides of the lower casing 12, and one of the conductive clamping plates 16 is integrally formed with one of the power conductive plates 15, and another conductive clamping plate 16 is connected to another power conductive plate 15 for receiving different polarities of the power supply of the power conductive plates 15 respectively, and such connection requires no soldering process. In addition, the upper casing 11 is covered onto the lower casing 12 and provided for covering all components installed in the lower casing 12, and an opening 111 is formed at the top of the upper casing 11, and the press button 13 is installed at the top of the upper casing 11 and connected to a power supply module (not shown in the figure) through the opening 111. When a user switches the press button 13 to control the power supply module, the conductive clamping plates 16 can be set to a power connection status or a power disconnection status. Therefore, manufacturers can assemble a plurality of switch modules 1 into the casing of a power extension cord, and insert the conductive clamping plates 16 of every switch module 1 into a socket hole, such that users can plug a power cord connector of an electronic device into a socket hole.
In FIGS. 1A and 1B, the aforementioned method can avoid the issues brought by the soldering process, but the power conductive plate 15 and a connecting portion 151 are integrally formed as a whole, and thus it is necessary to remove the material (as indicated by the dotted line 151A of FIG. 1B) between two adjacent the connecting portion 151 during a stamping process. As a result, the manufacture wastes too much material, and the price of the switch module remains relatively high (because the price of raw material increases day after day.) Since the conventional switch module has many soldering points, and each soldering point has the aforementioned problems, therefore the defective rate of the switch modules is high. Furthermore, the aforementioned assembling process includes a manual soldering procedure, not only slowing down the assembling speed and incurring a high labor cost, but also causing pollutions to the environment as well as the components installed in the switch module. Some manufacturers adopt the integrally formed power conductive plate and conductive clamping plate, but it will waste too much material. Therefore, it is an important subject for related manufacturers to design and develop a switch module to overcome the aforementioned problems and provide an automated production without requiring any soldering process.